1. Field of the Disclosure
The subject disclosure relates to systems for scavenging ullage from center wing tanks (CWT) in an airplane, and more particularly to an improved system for scavenging the ullage, then reducing the levels of reactive components, and returning the resulting inert air to the ullage space of the CWT.
2. Background of the Related Art
Center wing tanks (CWT) are used to hold fuel for airplanes. Although airplanes run on liquid fuel, the CWT generally contain some amount of air known as ullage. During long flights, for example, a large amount of fuel is consumed to create space in the CWT filled by ullage. If left alone, the ullage would not only be a gas rich in fuel vapors but include ample oxygen present in the ambient ullage air intake flow. When the ullage contains these reactive components (e.g., oxygen and/or fuel vapors), fires and explosions become possible.
To alleviate the hazards associated with ullage, some systems have been developed to fill the ullage space of the emptying tank with nitrogen rich air or an otherwise inert gas. Typically, electrically powered air pumps circulate the replacement air into the ullage space. Several techniques have also been developed to remove the reactive components from the ullage. For example, U.S. Pat. No. 7,694,916 to Limaye et al. (the '916 patent), issued on Apr. 13, 2010 and incorporated herein by reference, shows a catalytic reactive component for reducing reactive components.